Are you saying the amount of data in your http request using LHTTP_Get is more than 254 characters?

You are not talking about the amount of data returned, correct?

If you can open the LHTTP_Get FB and see the SCL logic and interface, feel free to copy/paste into a new FB where you adjust the data:STRING to data:WSTRING and handle any changes in the logic to support the change.

There is a support link provided in the documentation for having Siemens Support provide specific help:

https://sieportal.siemens.com/en-ww/mysieportal/support-requests/create

PAdler

We are using TIA Portal V16 and the PostPut block from the LHTTP library to send JSON data from an S7-1500 PLC (1517F-3 PN/DP) to an external HTTP server.

When sending a JSON message stored in a STRING variable with a length of up to 254 characters, the request is successfully processed, sent to the server, and the server responds as expected.

However, if the message exceeds 254 characters, the HTTP request fails. We have unsuccessfully tried the following alternatives:

• Using a longer STRING (e.g., STRING[500]) → fails with error 16#8205 (Invalid parameter length)
• Using WSTRING type → fails with error 16#8204 (Wrong parameter type)

Our message is a JSON string longer than 254 characters, and we need to send it as a single HTTP request.

Questions:

1. Is there an officially supported way to send a message longer than 254 characters using the PUTPOST block or another HTTP block?
2. Can the message be sent in a different way than using a string variable, e.g., as an ARRAY[0..n] OF CHAR via the data input, and if so, what is the maximum supported length of this array?
3. Are there any recommended or documented best practices for sending long strings (e.g., JSON/XML) from a PLC via the HTTP protocol?